ranger



May 10, 1932. R. H. RANGER 1,857,329

PICTURE TRANSMISSION Original Filed April 13, I926 2 Sheets-Sheet l E It,m Q R.

IIIIIIIIIIIIP R v J l .2

[I I 400'" 20o l l l i l l f 0 2 1 1 9. 3 14 INVENTOR RICHARD H. RANGERM ATTORN EY May 10, 1932. R. H. RANGER 1,357,329

PICTURE TRANSMISSION Original Filed April 1926 2 Sheets-Sheet 2 INVENTORRICHARD H. RANGER dam,

A ORNEY Ill Patented May 10, 1932 UNITED STATES PATENT OFFICE RICHARD H.RANGER, OI NEWARK, NEW JERSEY, ASSIGNOB TO RADIO CORPORATION 01 AMERICA,A OOBPORATION OI DELAWARE PICTURE TRANSMISSION Application med April 18,1926, Serial). 101,611. Renewed August 13, 1930.

My invention relates to the transmission of pictures over a signalingchannel and particularly to refinements in the method thereof.

An object of my invention is to provide an improvement in picturetransmission processes.

Another object of my invention is to provide means for increasing thedetail of a transmitted icture.

Another oliject of my invention is to produce a picture composed ofparallel lines of dots, dashes and spaces in which alternate linesproduce an effect of a darker tone than the intermediate lines.

In my copending applications, Serial Nos. 695,17 5 filed February 26,1924, and 726,235 filed July 16, 1924, I have disclosed twomodifications of a process for the transmission of pictures over asignal channel. In these processes, synchronized scanning andreproducing means are provided whereby the lights and shadows of apicture are analyzed by a photo-cell and the total amount of lightenergy therefrom, along a given narrow line,

- is integrated to,pr0duce a series of current pulses corresponding inspacing, or in both length and spacing, to the mean efi'ectiveillumination from the picture. pulses are then transmitted over aconvenient signal channel and are caused to actuate a pen, moving insynchronism with the scan: ning means of the sender, whereby rows ofmarks are made upon paper corresponding to the light tones of theoriginal picture. It has been found that excellent reproduction ofpictures may be obtained by the process as disclosed in the mentionedapplications.

As in the above named applications, the

system is herein described as relating to the transmission orduplication of picturesor thelike. but it is to be understood that theinvention is not limited to the transmission of pictures'onlybut anyother type of subject matter such as motionpicture films, newspapers,financial statements, fashion plates,

and the like, may be transmitted and are in tended to fall within thescope of the term pictures.

My present invention, however, provides means for making a furtherimprovement in These currenting description when read in connection withthe accompanying drawings, wherein:

Figure l is a diagrammatic representation of circuits and apparatusembodying my invention and 4 Figure 2 is a modified form of circuits andapparatus embodying my invention.

Figure 3- is a dlagrammatic representation of the circuits of my hotomodulator of the previously mentione applications with a form of mypresent invention embodied -there1n.

Figure 4 is a diagrammatic indication of the difference between theproduct as formerly made and a product of my present invention and,

Figure 5 is a picture reproduced according to my'invention.

Broadly the process of my invention consists in modifying the responseof the photocell and amplifier above at the sending apparatus in such wathat atsuccessive intervals the pulses pro uced correspond to,thosewhich would normally be produced from a print having variations ina high light-key rate, and at another instant, variations in a lowlight-key with respect to the actual'density at the particular point.This in efi'ect is equivalent to varying the length of spaces, or thelength of both the spaces and dots,

corresponding to a given light intensity of the print.

In my first indicated embodiment the change in efiective intensityoccurs at the end of the line of scanning so that alternate cross linesof the recorded picture are alternately til ' pearance characteristic ofthe lighter than, and heavier than, the normalline. rovided b m originals stem as revious l disclos l- It is, howgver, obvibus that tli linesgives apicture tone value which is very closely equivalent to thepicture tone value of two lines of the former t pe, of recorded picture.It has, however, t e great advantage of giving much more sharply markedout image lines, much better much wider range of tone values. Likewiseit tends to obviate the coarsel granular apfirst too strictly regularprints produced by the processes of the above mentioned applications.

The change ma be produced by any convenient means an at any convenientrate of speed. It may be produced by a cyclic change ,in li ht intensityof the scanning light. It

may produced by a small fluctuating light impinging directly upon thephoto-cell, or it may be produced by a change in the grid bias of anyconvenient amplifier triode incorporated in either the transmitting orreceiving apparatus. Likewise the change in intensity, which may becalled for convenience a bias, may be produced by a potentiometercontrol upon the grid of an amplifier triode,,which shifts in value bythe required amount at the end of each line of scanning under thecontrol of the synchronous scanning-drive mechanism or it may be shiftednonsynchronously by anyconvenient device. A convenient means forproviding this bias isshown in Figure 1. A photo-cell 1 is provided andconnected to a battery 2 in series with an output resistance 3.Amplifying means as shown in the previously mentioned applicationsamplifies the photo-cell output through the agency of a triode amplifier4.

Any convenient grid biasing means for the triode 4 may be provided,such, for instance, as a resistance 5 in the filament su ply leads. Apair of potentiometers 6 and are then connected to the biasingresistance 5 and provision made for setting the contacts thereon to giveany desired negative bias to the grid of the triode 4, by way of thephoto-cell circuit. Leads'are takenfrom the contacts of thepotentiometers 6 and 7 to contacts of a relay8, the tongue of whichisconnected to the photo-cell circuit and thereby to the grid of thetriode4. The coil of the relay 8 may be energized by any convenientportion of the circuits so that it will swing from one contact to theother at. regular intervals. This interval may be, as abovedescribed,-that of the successive cross-wise movements of the scanningmeans, in which case alternate cross lines. will be predominantlyalternately light and heavy asdescribed. The potentiometers may then beadjusted by trial. One, No. 6, for instance, may be set to make the gridsomewhat less negative than would normally be done, whereby a heaviercurrent flows in the e heaviness of marking of two such detail and atriode4 under a given illumination of the photo-cell 1. This reduces arelatively greater number of pu ses than normally, and

therefore, a heavier line in the receiving device. T e otherotentiometer may then be set to ma e the gr1d somewhat more ne ativethannormally, and in consequence ,un er its control rather less. currentwill flow thr ugh the triode 4 with a given illumination of thepiloto-cell 1, and therefore, a 1i hter line will produced at therecorder. lternation of control of the grid bias between the twopotentiometers by the swing of the tongue of the relay 8 then gives thedesired alternation between predominantly light and predominantly darklines in the recorder.

This is conveniently shown by the representation of Figure 4 the upperportion a of which indicates the character of marks produced by myinvention as described in the previously mentioned applications whilethe lower portion 6 indicates the result of my present invention. Asindicated, the portion (1 consists of marks which may vary in length andin spacing to vary the tone value of the reflected light, while portion7) shows marks varying in average density in alternate lines. Thisrepresentation is purely diagrammatic in character since it has beenfound impossible to produce by hand a picture of the character producedmechanically by the device of my invention.

s The actual resultproduced by the apparatus of my invention as hereindisclosed is shown in Figure 5 which has been transferred to thedrawings of this application by photomechanical processes due to thefact that a picture of the type shown by Figure 5 cannot be producedmanually. The picture record per se, as an article of manufacture, hasbeen more particularly described, claimed and set forth inapplicantsdivisional application Serial No; 338,073, filed Feb. 7, 1929.

The embodiment shown in Figure 1 and above described produces a markedimprovement in the character of the reproduced picture. It is, however,rather more regular in its variation between light and dark lines thanis desirable.

The embodiment shown in Figure 2 provides a random change frompredominantly light, to predominantly dark lines and a change at ahigher frequency than the embodiment of Figure 1, so that the change mayoccur in a random distribution in the course of a marking of a givenline.

In this embodiment a photo-cell 1 is provided as beforewith battery 2,output resistance 3 and triode amplifier 4. As before, a grid biasresistance 5 is provided. A potentiometer 9 is provided and connectedacross the ends of the resistance 5. In parallel with the potentiometer9 is connected a second potentiometer 11 which is designed to have itscontact arm continuously rotated by negative bias which can be furnishedby means of a motor 12 or other convenient device. An additionalpotentiometer 14 is provided and connected betweenthc contacts of thepotentiometers 9 and 11 with its own contact connected to the photo-cellcircuit and thereby, to the grid of the triode 4.

In the operation of this device the setting of the contact of thepotentiometer 9 determines the average grid bias. The rotation of thecontact of the potentiometer 11 then causes alternately the maximum, andminimum the biasing resistance 5. These maxima or minima are not,however, impressed di rectly upon the grid of the triode 4,

but are applied to oneterminal of the potentiometer 14, to the otherterminal of which is applied the meaneifective bias produced by thepotentiometerfi. The bias upon the contact of the potentiometer 14 thenfluctuates about the value set by the potentiometer 9 by an amountdepending upon the a the potentiometer 14 as will be obvious of in--value of the drop in the resistance 5, swing of the rotatingpotentiometer and the setting of spection of the diagrammatic showing.

By either of these means the desired fluctuating marking line density isobtained at the reproducer and the desired improvement in detail andsharpness of outline of the reproduced print occurs.

By Figure 3 of the arrangement herein- .disclosed I have shown theapplication of the equally simple to combine therewith .the-

showing of Figure 2 or other such modifications of the invention as mayreadily suggest themselves to those skilled inthe art to which theinvention relates.

While I have shown but two embodiments of my invention in the foregoingdrawings and de scriptionsit is capable of various modifications'therefrom without departing from the spirit thereof. and it is desiredtherefore that only such limitations shall be imposed thereon as arerequired by the priorart or indicated by the appended claims.

I claim as my invention:

1. In combination, an amplifier-devices, means for producing potentialchanges thereon, and means for producing at time periods of relativelywide separation an abrupt its conta'ct arm to takecurrent.

below the normal bias for producing at said predetermined rate anincrease above normal output and a decrease below normal output from theam lifier.

. 2. In combmation, a photo-cell device for.

convertingc'changing light values into-proportionately changing electriccurrents, an

amplifier device connected with said photocell, means for impressing theoutput currents from sald hoto-cell upon said amplithrough, and meansfor intermittently applying to said amplifier device,biasing otentialsof two limital values above. and elow the normal biasin otentials foralter nately increasing ant? ecreasing the amphfier response from thenormal.

3. The method of reproducing pictures and the like, which comprises thestep of intermittently modifying an electriccurrent .the number of suchmodifications perunitof time being progressively varied according to thelight intensity of a unit of the picture to be reproduced,andi'n'dependently cyclically modifying said electric current.

her for controlling the current flow there- 4. A method of reproducingpictures 'and the like which comprises the step of progressivelyprojecting upon a light sensitive element, light from different sectionsof the picture to be reproduced. and utilizing the changes in said lightsensitive element thereby produced to produce intermittent changes in anelectric current in a manner to cause the number of said changes perunitof time to vary according to intensity of light falling upon saidelement, and also cyclically varying the base line value of saidelectric -5. A method of reproducing pictures and the like whichcomprises progressively projecting upon a light sensitive cell lightfrom different sections of the picture and utilizing the variations insaid cell thereby produced to control an electric current in a manner tovariations per unit of time in accordance with light intensities ofsuccessive portions of the picture, rythmically varying theeffectiveness of light intensities in producing said variations, andsuitably reproducing the picture from such variations.

7. A method of expressing variations of light intensity in terms ofelectric current which comprises translating varying light intensitiesinto current impulses, light inchange in the grid bias to points aboveand tensities at one end of the scale being represented by impulses ofsubstantially uniform duration separated by periods exceeding induration thedurationiof said im ulses, and light intensities lying onthe ot er end of said scale bein represented b impulses separated byperiods of substantia ly uniform duration,- the duration of saidimpulses exceeding the duration of the separating peri'ods, andcyclically varying the effective response to light values, whereby theimpulses are alternately. lighter than, and heavier than, the normalvalue required to represent said light intensities.

8. A method of representing variations of li ht intensity in terms ofelectric current which comprises normally producing current im ulses ofsubstantially uniform duration and separated by spacing periods ofsubstantially uniform duration, the duration of the current impulseshaving a predetermined ratio to the duration of the spacing periods, fora predetermined intensity of light, and varying said ratio in thedirection of increase for variations of light intensity in one directionaway from-said predetermined value of light. intensity and varylng saidratio in the direction of decrease for variations in light intensity inthe other direction from said' predetermined value of light intensityand cyclically varying the degree-of response to J a predeterminedlight.

9. In apparatus for translating variable light intensities into electricimpulses, the combination of means for producing periodic impulsesnormally of substantially equal duration and separated by periods ofsubstantially equal duration, and the duration of the impulses normallybeing equal tothe duration of the separating periods, and means for varing the duration of either of said periods an means cyclically varyingthe degree of response to a given light value.

10. In apparatus .for translating variable light intensities intoelectric impulses, the combination of means for producing periodicimpulses normally of substantially equal duration and separated byperiods of substantially equal duration, and the duration of theimpulses normally being equal to the duration of the separatin periods,and means for varying the duration of either of said periods,independently of the other, and means for cyclically varying a responseto a given light intensity.

11. In modulating apparatus, the combination of a plurality of means forstoring predetermined quantities of electricity, means for supplyingelectricity to said plurality of means at a predetermined normal rate,and means controlled by light intensity for varying the rate of supplyof electricity to one of said storing means independently, and means forcyclically varying the rate of response to said-light intensity of saidlight controlled means.

tricity to the ot er of said storing means in accordance with variationsin intensity of light lyin on the other side of said predetermined ightintensity and means for cyclically varying the controlling efiect ofsaid light intensity.

13. The method of reproducing pictures and the like which comprisesactivating the photo-electric element in accordance with variations oflight and shade of a picture surface, intermittently modifying thepotential on an amplifier in accordance with the light reaching thephotoelectric element, and abru tly changing the biasing potentialapplied to said amplifier from oneto another predetermined value foraccentuating the current flow therethrough during certain time periodsand retarding the current flow therethrough during other time periods.

14; The method of reproducing pictures and the like which com risesintermittently and progressivelymodig'ing an electric current inaccordance with the tone intensities of elemental areas of a picture tobe reproduced, and" in independently andabruptly which comprisestranslating the elemental tone intensities of a picture into varyingstrength electric current impulses, controlling an amplifying system inaccordance with the strength of said varying impulses, and

time

abruptly increasing and decreaslng to two predetermined limited valuesat predeter-- mined time intervals the effect of said first namedcurrent impulses upon said amplifying system, I I

16. Amodulating apparatus for facsimile transmission which includes, incombination, means for translating varying intensities of light andshade on a picture surface intovarying strength electric currentimpulses, means for amplifying said varying strength electric currentimpulses, and independent means operable at predetermined time intervalsfor increasing and decreasing abruptly the amplification of said firstnamed electric current impulses to limits above and below normal.

1,7. A photo amplifying system including photo-electric means fortranslating varying intensities of light and shade on a picture surfaceto be transmitted into varying strength electric current impulses, anamplifier, means for impressing said varying strength electric currentimpulses directly upon said amplifier and varying the current outputthereof in accordancewith the strength of the current impulses appliedthereto, and independent potentiometric means connected with the inputof said amplifier for cyclically increasing and decreasing the currentoutput from said amplifier in a predetermined spaced relationship forbringing the amplified current impulses above the normal tone valueduring certain predetermined periods and below a predetermined tonevalue at other predetermined A periods.

18. A photo amplifying system including, in combination, aphoto-electric cell for trans lating varying intensities of light andshade on elemental areas of a picture surface into varying strengthelectric current impulses, a vacuum tube amplifying system foramplifyingsaid impulses, means for impressing said impulses upon the input.circuit of said vacuum tube amplifying system and controlling theamplified currents in accordance with the strength of the appliedcurrent impulses, a plurality of independent biasing resistancesconnected with the input of said amplifying system, and means foralternately and cyclically connecting said resistances in the inputcircuit of said amplifier for increasing and decreasing the current flowthrough said amplifier so as to cyclically bring the current flow aboveand below a predetermined value for the particular tone intensity of thepicture surface.

19. The method of reproducing pictures which comprises producingelectric currents of values proportionate to the intensity of light andshadow of elemental areas of a record surface which is to be reproduced,and

independently and abruptly modifying the electric currents produced forproducing during one predetermined time period increased output currentsand for producing during like predetermined periods decreased outputcurrents.

20. The method of reproducing pictures which comprises progressivelyvarying the strength of an electric current in accordance.

with the intensity of light and shadow of elemental areas of a picturesubject which is to be reproduced, and intermittently and alternatelyvarying independently of the picture to be reproduced the electriccurrents to increase the current strength to a predetermined valueduring certain predetermined time periods and to decrease the currentstrength to a predetermined value i like predetermined time periods.

21. In a double setting system for the reproduction of visible subjects,an amplifier and-intermittentl operable means connected with said amplier for alternately placing the output energy level therefrom at prede-.

termined points above and below the. norm output energy for impressedinput energy.

22. In a double setting system for the reproduction of visible subjects,an amplifier and 23. In a double setting picture reproducing system, anamplifier, an input circuit associated therewith for applying tosaidamplifier varying potentials corresponding to signals for amplification,and intermittently operable means for changing the output energy fromsaid amplifier irrespective of the input energy for producing forpredetermined time periods output energy above and below the normaloutput energy producible from normal amplification for said input energyv 24. In a double setting picture reproducing system, an amplifier,light translating means for converting varying intensities of light andshadow on a'record surface of which an image is to be transmitted intoproportionate strength electric current impulses, means for impressingsaid electric current impulses .upon the mput circuit of said amplifier,and

proportion to preestablished intensities of' light and shadow upon saidamplifier, means for causin a response from said amplifier over a preetermined time period of a value below the normal response for saidimpressed signals, means for causing a response from i said amplifierduring a second similar predetermined time period of a value above thenormal response for said impressed impulses, and abruptly operable meansfor changing the response of said amplifier between said Values aboveand below the normal output therefrom so as to produce a resultingeffective output which is substantially linear.

26. In a system for producing the effect of linear response from a phototube amplifying system for amplifying currents produced in accordancewithwarying changes in light intensity upon elemental sections of arecord surface of which an image is to be transmitted,

a light converting element for converting the i a changes in lightintensity upon elemental sections of a record surface intopsigportionate strength ePectric current impu an am-- plifying systemfor amplifyi the produced electric current impulses, an means inte'r-,mittently operable at a predeterminedslowly changin rate for chan ingthe characteristic curve 0 operation of t e amplifying system betweenlimitlng values above and below the normal operating characteristicwhereby the resulting efiective output from theamplifying system issubstantially linear.

27 In combination with picture transmitting apparatus, a lighttranslating element, an amplifier, and means operable alternateiiy atpredetermined time periods correspon ing tothe time period re uired toscan each line of the picture record y said light translating elementfor abru tly changing the out ut level of said ampli er to values abovean below the normal out ut level.

. 28. In combination wit a picture reproducing system, a lighttranslating 1 element adapted to be move in a line for ne mannerrelative to a record subject of which an image is to be reproduced forconverting lifght values of successive elemental areas 0 the pictureinto proportionately varied electric current impulses, an amplifier foramplifying said produced electric 'current impulses, and means operableat the end of each line of picture scanning for abru tly changing theoutput level of said ampli er to a value above or below the normaloutput level thereof. e

29. The method of reproducing picture records which comprises scanning arecord subject by a li ht translating element in a series of parallellines to produce electric current impulses. of intensities varying inaccordance with the intensity ofv light and shadow on successiveelemental areas of the record of whichthe electro-optical image is Idesired, amplifying the produced electric current impulses, and changingat the end of each line of scanning the normal bias upon the amplifyingsystem between values above and below normal to produce increasedcontrast and sharpness of detail in a icture record reproduced from theamplifie signalling impulses.

RICHARD H. RANGER.

